An 11-year-old girl is believed to have made the horrific discovery when she opened the plastic bag and saw a human ear.
Police later confirmed the head belonged to a Caucasian male, possibly aged between 30 and 60.
Seven of the man's upper front teeth were missing - and had been for some time - but the man did not wear a plate or dentures, forensics have revealed.
His other teeth were also in a poor condition.
Forensic officers have searched several locations since identifying the man, including an apartment in East Perth where the he is believed to have lived.
The matter is being treated as a homicide.
-AAP